Dark Banquet - Bill Schutt [110]
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‡53 Less well known is the fact that the Arab physician Ibn al-Nafis (1213–1288) had described much of this dual-circuit pump four hundred years earlier.
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*54Besides connective and nervous tissue, there are two additional tissue types: epithelial tissue, which covers surfaces and lines hollow structures, and muscle tissue, unique for its ability to store chemical energy, then convert it into the energy of motion as the tissue contracts in size.
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†55 The flexibility of cartilage, another type of connective tissue, comes from a gel-like matrix, which is basically bone matrix containing bendable protein fibers instead of calcium and mineral salts. Tendons and ligaments, which connect muscle to bone and bone to bone, respectively, are also structures composed of connective tissue, and they get their strength from the tough, wirelike fibers found embedded within their matrices.
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*56Like other pressure measurements (e.g., barometric pressure), blood pressure is measured in millimeters of mercury, so that a systolic pressure of 110 represents a force applied to the blood vessels’ inner walls equivalent to one that could raise a thin column of mercury 110 millimeters in height (were that column of mercury sitting at sea level in a U-shaped glass tube).
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*57Oxygen (which is actually carried around inside red blood cells) and nutrients diffusing in this manner are said to be following a concentration gradient, moving from areas where they’re in a higher concentration (the blood) to areas where they’re less concentrated (e.g., oxygen-and nutrient-starved tissues and cells).
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*58Like vertebrate blood, hemolymph does carry nutrients, hormones, and metabolic waste. It also functions in clotting and the immune response.
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*59Hemoglobin’s high affinity for carbon monoxide, coupled with the fact that the gas is odorless, are two major reasons why several carbon monoxide detectors are an absolute must for every home. In fact, if you’re reading this and don’t have a CO detector, put this book down and go buy one (or order it online). It’s that important.
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*60Blood can be separated into its three major components by spinning it in a centrifuge. A band of erythrocytes (making up 44 percent of the blood volume) will settle to the bottom of a centrifuge tube, with a thin band (1 percent) of leukocytes and blood platelets (known as the buffy coat) sitting above that. The yellow-colored plasma rests on top, making up the greatest portion (55 percent) of the blood volume. By measuring the hematocrit, the proportion of the spun blood composed of red blood cells, doctors can test for conditions like anemia (a decrease in red blood cells) or polycythemia (an increase in red blood cells). For those of you who may be wondering, the blood is prevented from clotting during this procedure by spinning it in heparinized tubes.
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*61For documentary footage of a large, alien macrophage, I recommend watching the 1958 film The Blob (starring Steve McQueen). By doing so, you can get a pretty good idea of how phagocytosis works.
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*62This is pretty much why you don’t catch the same strain of flu twice and also why you need a new flu shot every year: new viral strains evolve new surface proteins (antigens) that go unrecognized by memory cells or circulating antibodies.
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*63Back then, people ascribed to the concept of vitalism, in which all creatures possessed an inner force responsible for their specific traits (like bravery in lions or a lust for gold in those working in the insurance industry).
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*64Mauroy’s dark-colored urine probably resulted from the chemically altered hemoglobin, released by transfused red blood cells blasted apart by the man’s immune system. Perhaps owing more to luck than anything else, Mauroy began to recover